Hired on Jan. 12, 2012, as the offensive line coach and offensive coordinator, he is on the verge of becoming head coach Jason Garrett's right-hand man and taking over his offense.

Callahan has gained so much trust in the organization, Garrett and owner Jerry Jones openly talk about him taking over as the play-caller on game day, the job Garrett has had for the previous six years.

Even if they won't come out and explicitly announce the transfer of that duty, the Cowboys' trust in Callahan is clear.

"Bill wouldn't be on the staff if we didn't have shared values," Garrett said this week. "My respect for him as a person and a coach is off the charts. ...He's been with us for a year now. He understands what we've done on offense. He's brought a lot of stuff to our offense."

Callahan might not have seemed a no-brainer choice at first for new play-caller. Behind his offensive line last year, the Cowboys ranked 31st in rushing.

But Callahan has a long NFL résumé, dotted with highlights. In Oakland, he produced both a No. 1 passing team (in 2002 with league MVP quarterback Rich Gannon) and a No. 1 rushing team (in 2000, behind 1,000-yard rusher Tyrone Wheatley and backup Napoleon Kaufman).